We want to study how the green alga Ulva mutabilis (or sea lettuce) can take up CO2 from the surrounding sea water. This process is relevant for many algae species and determines the efficiency of photosynthesis, the process that utilises solar energy and CO2 to produce sugars and the oxygen we breathe. Our research will help to link this process to the formation of blooms and the growth of algae. To identify and characterise factors in the transport of CO2 and the conversion to bicarbonate (HCO3-), we will use different but complementary approaches. First, we will inspect which genes are expressed more when Ulva is transferred from a high to a low or very low CO2 environment. These genes are likely positive factors in increasing the uptake of CO2 from the environment. Second, we will make mutations in the DNA of Ulva using UV-B illumination. If a gene involved in CO2 metabolism is affected, we expect to identify this through an altered growth pattern in low CO2 environment compared to a control. Finally, we will generate Ulva lines which are mutated in specific genes related to adapting to a low CO2 environment and characterise if growth or photosynthetic efficiency is affected in these lines. This research will help us to understand the growth and development of Ulva, which is common for coastal ecosystems and is used as a food and feed source, but also for bioremediation, in integrated aquaculture systems and as a putative biofuel.